The use of transformers in electrical systems is well known in the art. Transformers are commonly used to provide galvanic isolation for wires carrying signals over substantial lengths. The operating range over which a conventional transformer is capable of providing linear, distortionless, and unattenuated signal transfer, however, is limited by the magnetic saturation of the transformer's core. Saturation occurs when a transformer is driven to induce a net flux density higher than its core can support. It is known from transformer theory that flux density is proportional to the ratio of winding voltage to frequency. Thus a transformer will tend to saturate at higher voltages and lower frequencies.
In audio applications, for instance, the limitations attributable to core saturation are particularly apparent in the performance of commercially available miniature transformers at lower signal frequencies. One known alternative for improved low-end frequency performance is to use a larger transformer. In applications where space is at a premium, such an alternative is often not a viable one. Moreover, larger transformers are heavier and costlier.
Another alternative is to avoid transformer coupling altogether. Transformerless systems, however, lack the advantages of galvanic isolation and are thus more susceptible to damage from connection faults, for instance, as where signal wires are accidentally shorted to nearby sources of DC current. Transformerless systems are also more susceptible to electro-static discharge (ESD) and interference from other signal sources, and provide less common mode rejection.
The present invention provides a transformer compensating circuit which improves the linearity of transformer operation. The low-end frequency response is markedly improved while harmonic distortion is reduced. Moreover, input and output impedances are also linearized.